The present invention relates to an ink jet recording head in which a part of each pressure generating chamber communicating with nozzle orifices for ejecting ink droplets is formed with a vibration plate, a piezoelectric element is provided on the vibration plate interposed, and an ink droplet is ejected by a displacement of the piezoelectric element and a method of manufacturing the recording head, and an ink jet recording apparatus.
The ink jet recording head in which a part of each pressure generating chamber communicating with nozzle orifices for ejecting ink droplets is formed with a vibration plate, and the vibration plate by the piezoelectric element is deformed to pressurize ink in the pressure generating chamber to eject an ink droplet through the nozzle orifice, is known. This type of recording head is categorized into two types of recording heads; one uses the piezoelectric actuators of the longitudinal vibration mode in which the piezoelectric element axially expands and shrinks, and the other uses the piezoelectric actuators of the flexural vibration mode. Those types of recording heads have been put into practice.
The former recording head is advantageous in that the recording head suitable for the high density printing may be manufactured since the volume of the pressure generating chamber is varied by bringing the end face of the piezoelectric element into contact with the vibration plate. However, it has a difficult step of cutting the piezoelectric elements in a comb shape in alignment with the pitches of the nozzle orifice array, and needs another step of positioning and fixing the cut piezoelectric elements to the pressure generating chambers. In this respect, the manufacturing process is complex.
The latter recording head is advantageous in that the piezoelectric elements may be formed on the vibration plates in a relatively simple manner that a green sheet of piezoelectric material is bonded onto the vibration plates in conformity with a shape of the pressure generating chambers, and then baked. However, this recording head is disadvantageous in that since the flexural vibration is utilized, an area of some extent must be secured for each the piezoelectric element. Accordingly, it is difficult to array the piezoelectric elements at high density.
To solve the disadvantage of the latter recording head, there is proposed a technique in which a piezoelectric layer is uniformly formed over the entire surface of the vibration plate, and the piezoelectric layer is cut by a lithography process to form individual piezoelectric elements for each pressure generating chamber in accordance with arrangements of the pressure generating chambers (see JP-A-5-286131).
This technique enables to eliminate the work of bonding the piezoelectric elements to the vibration plates. Accordingly, the piezoelectric elements may be manufactured by a precise and simple process, using the lithography process. Additionally, the piezoelectric element is thinned and hence driven at high speed.
In such an ink jet recording head, the pressure generating chambers are formed penetrating the passage forming substrate in a manner that the passage forming substrate is selectively etched by anisotropic etching process from a surface of the passage forming substrate opposite to the piezoelectric-elements to the vibration plate.
When the anisotropic etching process is carried out in the form of a wet etching process using an alkaline aqueous solution, the alkaline aqueous solution or etching reaction products penetrate through the vibration plate to damage the piezoelectric elements, at the end of the etching process.
In the dry etching process, the etching is terminated indefinitely, therefore it is difficult to control the width of the vibration plate side of the pressure generating chamber. Accordingly, the pressure generating chambers cannot be formed with high accuracy by the dry etching process.
Further, in such an ink jet recording head, the pressure generating chambers are formed by the etching after the piezoelectric elements are formed. Accordingly, a position of the vibration plate side of the pressure generating chamber is instable by the dispersion in verticality of the pressure generating chambers. An accuracy of a relative position shift of the piezoelectric element to the pressure generating chambers is low, so that the ink ejecting characteristic and stability are low.
An object of the present invention is to provide an ink jet recording head having highly reliable piezoelectric elements and the improved ink ejecting characteristic and stability and a method of manufacturing the same, and an ink jet recording apparatus.
In one broad aspect of the invention, there is provided a first ink jet recording head having a passage forming substrate made of a silicon monocrystalline substrate including at least one pressure generating chamber communicating with a nozzle orifice; a vibration plate provided on a surface of the passage forming substrate; a piezoelectric element provided on the vibration plate having a lower electrode film, a piezoelectric layer and an upper electrode; a wide portion provided in the pressure generating chamber on a side of the vibration plate, extending in a longitudinal direction of the pressure generating chamber, a groove formed on a side of the wide portion, extending in a longitudinal direction of the wide portion; and an etching stop layer provided in the groove, defining a side wall of the wide portion as viewed in the width direction thereof to restrict the spread of the etching in the width direction.
In the first ink jet recording head, the width of the wide portion of the pressure generating chamber is restricted easily and reliably by the etching stop layer. As a result, the pressure generating chamber is manufactured highly accurately.
In a second ink jet recording head, the etching stop layer has each an insulating property.
In the second ink jet recording head, since the etching stop layer has an insulating property, no current leaks to the ink in the pressure generating chamber.
In a third ink jet recording head, the etching stop layer is made of the same material as that of a part of the vibration plate.
In the third ink jet recording head, the etching stop layer is made of the same material as that of a part of the vibration plate. Accordingly, the manufacturing process is simplified.
In a fourth ink jet recording head, the etching stop layer is made of silicon oxide.
In the fourth ink jet recording head, the etching stop layer is formed easily and reliably.
In a fifth ink jet recording head, the width of each groove is selected to be smaller in value than a value which is two times as large as the thickness of the etching stop layer.
In the fifth ink jet recording head, the etching stop layer is reliably formed within the groove.
In a sixth ink jet recording head, at least the vibration plate side of the pressure generating chambers are formed by anisotropic dry etching process.
In the sixth ink jet recording head, the piezoelectric element is reliably prevented from being damaged by an etching solution or etching reaction product, and the pressure generating chamber is manufactured highly accurately.
In another broad aspect, there is provided an ink jet recording apparatus being provided with the first to sixth ink jet recording head as described above.
The thus constructed ink jet recording apparatus is improved in the ink ejecting characteristics.
In yet another broad aspect, there is provided a method of manufacturing an ink jet recording head having a passage forming substrate consisting of a silicon monocrystalline substrate in which pressure generating chambers communicating with nozzle orifices are formed, and communicating with nozzle orifices are formed, and piezoelectric elements being formed on one of surfaces of the passage forming substrate with vibration plates interposed therebetween, each piezoelectric element including a lower electrode film, a piezoelectric layer and an upper electrode, which are formed with thin films formed by film forming and lithography processes. The method preferably comprises the steps of: forming grooves on both sides of each region at which the pressure generating chamber is to be formed in one of surfaces of the passage forming substrate, the grooves extending in the longitudinal direction; forming, in the grooves, etching stop layers which restrict the etching of the passage forming substrate; forming the piezoelectric elements by successively laminating the lower electrodes, the piezoelectric layers and the upper electrodes on one of the surfaces of the passage forming substrate with vibration plates being interposed therebetween, and by patterning the resultant structure; and forming the pressure generating chamber by etching out at least the vibration plate side of the passage forming substrate by the anisotropic dry etching process till the etching stop layers are exposed.
In the method of manufacturing the ink jet recording head, the spread of the etching in the width direction of the vibration plate side of the pressure generating chamber is easily controlled, so that the pressure generating chambers are manufactured highly accurately.
In another ink jet recording head manufacturing method, in the pressure generating chamber forming step, the passage forming substrate is subjected to anisotropic wet etching, and then anisotropic dry etching, thereby forming the pressure generating chambers.
In this method of manufacturing the ink jet recording head, the pressure generating chambers are formed by anisotropic wet etching and anisotropic dry etching. Accordingly, the time taken for etching may be reduced, and its manufacturing cost is reduced.
In yet another ink jet recording head manufacturing method, the etching stop layers have each an insulating property.
In the method of manufacturing the ink jet recording head, since the etching stop layers have each an insulating property, no current leaks to the ink in the pressure generating chambers.
In yet another ink jet recording head manufacturing method, the etching stop layers are made of the same material as that of a part of the vibration plate.
In the method of manufacturing the ink jet recording head, the etching stop layers are made of the same material as that of a part of the vibration plate. Accordingly, the manufacturing process is simplified.
In another ink jet recording head manufacturing method, the etching stop layers are made of silicon oxide.
In the method of manufacturing the ink jet recording head, the etching stop layers are formed easily and reliably.
In a further ink jet recording head manufacturing method, in the step of forming the grooves, the width of each groove is selected to be smaller in value than a value which is two times as large as the thickness of the etching stop layer.
In the method of manufacturing the ink jet recording head, the etching stop layers are reliably formed within the grooves.